A bolt-in cage is bolted to the chassis instead of welded. You bolt it into your existing car, drive your season, and unbolt it again when you change cars. That's the freedom that makes this line so attractive.
The major practical advantage: you don't have to completely strip your car, and the interior doesn't need to go to the paint shop. Our bolt-in cages are delivered painted, so much of the work involved in stripping, painting, and rebuilding is eliminated. This saves a significant amount of time, hassle, and cost. The cage is also detachable, so it can move with you to your next project as long as it fits.
What doesn't make a bolt-in cage inferior: every model in this line is developed for one specific car model and measured with 3D scanning, made from 25CrMo4 chrome-molybdenum, with the same precise welding that VA is known for. You're buying a ready-made cage that is correct for your car, not a design that still needs to be thought out. The only welding required during installation is the welding of a few reinforcement plates in the floor, where the footplates are secured. Otherwise, it's a matter of bolting.